Synthetic lubricants for aero gas turbines

ABSTRACT

A lubricant suitable for all the current specifications for turbine engines for supersonic transport aircraft is based on a hindered ester (e.g. PB 520) and contains an alkylated aromatic amine antioxidant, a copper passivator, and a neutral phosphate and an amine salt of a dialkyl hydrogen phosphate as load carrying additives. Optionally the lubricant may also contain a hydrolytic stability improver, a dispersant polymer, a lead corrosion inhibitor and a dialkyl phosphite load carrying additive.

United States Patent Byford et al. Oct. 21, 1975 [54] SYNTHETIC LUBRICANTS FOR AERO GAS 3,321,401 5/1967 Ford et al. 1. 252/56 S X TURBINES 3,347,791 lO/1967 Thompson et a1 252/56 S [75] Inventors: Derek Clark Byford, Stains; FOREIGN PATENTS OR L C TIONS Anthony Arnold John Mundye, Old 1,446,545 4/1965 France Windsor, both of England OTHER PUBLICATIONS [73] Assignee: P Petroleum Company Gunderson et al., Synthetic Lubricants (1962),

Llmlted, London, England page 210. [22] Filed: Apr. 10, 1974 Cohen et al., Ind. and Eng. Chem." Vol. 45, (1953), 21] Appl. No.: 459,765 Pages 176671775 Related US. Application Data Primary Examiner-De1bert E. Gantz [63] Continuation of Ser. No. 171,312, Aug. 12, 1971, Assistant ami er-I. Vaughn abandoned, which is a continuation-in-part of Ser. Attorney, Agent, or Firm-Morgan, Finnegan, Pine, No. 711,877, March 11, 1968, abandoned. Foley & Lee

[30] Foreign Application Priority Data [57] ABSTRACT 1967 Umtcd Kmgdom A lubricant suitable for all the current specifications for turbine engines for supersonic transport aircraft is [52] 252/325; g/ 2 based on a hindered ester (e.g. PB 520) and contains 1k 1' t' t' 'd t, 51 int. c1. ..Cl0M 1/44;C10M 3/38; 22 g g ;gg ii fg igz gg ffi g z f fi Field of Search CIOM of a dialkyl hydrogen phosphate as load carrying addifives. 3 3? 1 11-; flirir iiiiriir l ii fi sa11y1mprver,a 1se' UFITED ZTATES PATENTS 252/32 7 corrosion inhibitor and a dialkyl phosphite load 3,247,109 4 1966 enoit 3,247,111 4/1966 Oberright et al.. 252/347 Carrymg addmve 3,265,618 8/1966 Henderson 252/325 19 Claims, No Drawings SYNTHETIC LUBRICANTS FOR AERO GAS TURBINES This application is a continuation of our application Ser. No. 171,312 filed Aug. 12, 1971 which, in turn, was a continuation of our application Ser. No. 71 1,877, filed Mar. 11, 1968, both of said applications now being abandoned.

This invention relates to synthetic lubricants suitable for use under the severe conditions that exist in the op eration of modern aero gas turbine engines. More specifically, the invention is concerned with a lubricant of this type that is based on a thermally stable ester and which contains an additive package principally designed to impart good high temperature anti-oxidation, anti-corrosion, load carrying and hydrolytic stability properties to the basestock.

The problem of thermal stability in aero gas turbine lubricants can be satisfactorily handled by the use of certain hindered ester basestocks which generally also have good low temperature properties, being fluid in many cases at temperatures of -40C or below. A more difficult problem that has to be faced however, is the problem of oxidation stability and resistance to corrosion which arises owing to the fact that the lubricants have to operate at high bulk oil temperatures (about 200C) in contact with air. These conditions have the effect of greatly accelerating the oxidative deteriora tion of the lubricant which generally results in an increase in its viscosity and acidity, and corrosion of, or formation of deposits on, metal surfaces. Excessive increase in viscosity can lead to a restricted flow of lubricant to the engine bearings resulting in inadequate lubrication on starting and/or inadequate cooling during engine running. Deterioration of engine component condition by excessive corrosion or deposition can lead to malfunctioning of the moving parts, and excessive formation of oil insoluble materials can cause inadequate lubricator due to blockage of oil-ways. It is therefore very desirable that a lubricant of this typee should show no more than a slight tendency to increase in viscosity and acidity during service.

The performance of a lubricant in these respects is frequently assessed by submitting it to an oxidation/- corrosion test in which a sample of oil is maintained at a high temperature in contact with metal test pieces while a stream of air is bubbled through it for a prolonged period of time. Forms of this test are quoted in some Government and Engine Manufacturers specifications for aero gas turbine lubricants. In one form of this test, used to assess oils for high temperature applications, a sample size of 90 grams, a temperature of 400F (204C), an air flow-rate of 5 litres/hour and a test period of 72 hours are adopted as the test condi tions and 1 inch square plates of magnesium alloy, aluminium alloy, copper, silver and steel are used as the metal test pieces. A variation of this procedure uses a temperature of 425F (213C) and a test period of 48 hours. In these forms of the test, oils having poor resistance to oxidation at high temperature give high viscosity and acidity increase and tend to corrode certain of the metals, especially copper and magnesium.

Another serious problem that has to be faced in lubricants of this type is the provision of adequate load-carrying ability. This problem arises owing to the fact that ester basestocks that are sufficiently mobile to meet the low temperature requirements of lubricants of this type 2 (for example to permit easy starting of the engines in extremely cold conditions) are very thin and lack body under the high temperature operating conditions. Various methods are used for assessing the load carrying ability of such lubricants, for example the well known LAE gear machine. Government and engine manufacturers specifications usually specify minimum load carrying characteristics.

A further problem that is encountered in lubricants of this type is the problem of hydrolytic stability. This problem has been found to arise particularly in lubricants containing phosphates, e.g., tritolyl phosphate, especially when certain metal deactivators are present. One method of assessing the hydrolytic stability of an oil is to store a mixture of the oil and water at C with periodic agitation. The acidity of the oil is determined at intervals and the result may be reported either in terms of the acidity after a certain period of time, or as the time taken to reach a particular level of acidity.

Various additives are known for alleviating the above problems but in producing a final lubricant blend it is important that the particular combinations of base oil and additives used should be clean in use and not give rise to unacceptable levels of deposits on the engine components. One method of assessing the cleanliness of an oil in this respect is a Panel-Coking Test described later. An indication of the cleanliness of an oil can also be obtained by measuring the amount of insoluble material formed in the oxidation/corrosion tests described above.

Specifications for lubricants for modern aero gas turbine engines have been laid down by the British and United States Governments and by various manufacturers and designers of these engines, for example, Rolls Royce, Pratt and Whitney and General Electric. Unfortunately, the requirements of these bodies are not all the same and it is possible for an oil that meets one specification to be well outside the requirements of another specification. For example, British specifications in general tend to emphasise load-carrying ability rather more than American specifications and whilst it is possible by the appropriate selection of load-carrying additives to meet these stringent load-carrying requirements, the resulting oils may be unsatisfactory from the point of view of the very high resistance to oxidation and corrosion required by certain American specifications.

The object of the present invention is to provide a lubricating composition of low initial acidity having outstanding oxidation stability, corrosion resistance, hydrolytic stability and load-carrying ability, good low temperature fluidity, and which is clean in use, whereby it is suitable in these respects for the lubrication of modern aero gas turbine engines. A particular object of the invention is to provide a lubricating composition which meets or approaches all the varying such requirements of current (March 1968) specifications for turbine engines for supersonic transport aircraft.

According to the invention, there is provided a lubricating composition comprising an ester basestock consisting of a liquid neutral polyester that has been prepared by reacting together under esterification conditions and in one or more stages i. an aliphatic monoand/or polyhydric alcohol having 5 10, preferably 5 8, carbon atoms per molecule and having no hydrogen atoms attached to any carbon atom in a 2 position with respect to any 3 OH group and ii. an aliphatic monoand/or polycarboxylic acid having 3 12 carbon atoms per molecule, the basestock having dissolved therein:

a. l to 8, preferably 2 to 6, more preferably 3 to 5, wt of an alkylated aromatic amine antioxidant, particularly one where the alkyl groups have up to 14 carbon atoms,

b. 0.005 to 1.5, preferably 0.005 to 0.5, wt of a copper passivator,

c. 0.5 to 5.0, preferably 0.5 to 3.5, especially 1.0 to 3.0, wt of a neutral organic phosphate of the formula (RO)=;PO where the groups R are tolyl, phenyl or xylyl groups or alkyl, alkaryl or cycloalkyl groups having up to 10 carbon atoms, and

d. 0.005 to 0.5, preferably 0.01 to 0.1, wt ofa neutral salt of a dialkyl hydrogen phosphate of the formula (RO) P(O)OH, where R is an alkyl or cycloalkyl group having up to 10 carbon atoms, e.g. butyl or cyclohexyl, and an amine, preferably one having not more than 30 carbon atoms, especially a primary amine.

The lubricant described above has excellent oxidation stability, corrosion resistance, hydrolytic stability and load carrying properties. Its load carrying properties can be still further improved without substantial impairement of its hydrolytic stability by the addition of 0.005 t 0.2, preferably 0.01 to 0.1, wt of a dialkyl phosphite of the formula (R O) P(O)H where R is an alkyl or cycloalkyl group having up to carbon atoms, e.g. butyl or cyclohexyl.

If desired, the hydrolytic stability of the compositions according to the invention may be still further improved by the addition of 0.005 to 0.5, preferably 002 to 0.1, wt of a hydrolytic stability improver. Suitable ones are aliphatic or aliphatic/aromatic amines having up to 30 carbon atoms, or hydroxyl derivatives thereof, preferably tertiary amines. The most suitable amines for this purpose are those of the general formula R(R )NR where R and R are alkyl groups having 1 to 4 carbon atoms and R is an alkaryl, or hydroxy-substituted alkaryl, group having up to carbon atoms. A preferred compound of this type is 2.6-ditertiarybutyl- 4-dimethylaminomethyl phenol.

The above combination of additives and basestock provides a lubricant which is relatively clean in use but the cleanliness of the lubricant may be still further improved by the addition of a dispersant polymer, usually at a concentration of 0.01 to 50, particularly 0.01 to 1.0, wt. Dispersant polymer additives for lubricating oils are well-known materials and suitable ones include acrylate and methacrylate polymers, co-polymers of N-vinyl pyrrolidone with acrylates and methacrylates, and co-polymers of N-vinyl pyrrolidone with olefins as described in UK Pat. Specification No. 1,085,375. The polymers or co-polymers must of course be soluble in the ester basestock. The most suitable ones usually have molecular weights within the range 1000 to 1,000,000, especially 5000 to 500,000. The acrylates and methacrylates referred to are preferably those derived from acrylic or methacrylic acid and monohydric alcohols having 1 to 24, especially 4 to 18, carbon atoms.

Where the lubricant is intended for use in engines containing lead alloy components, it is desirable to include a lead corrosion inhibitor in the blend, usually at a concentration of 0.01 to 1.0, preferably 0.05 to 0.25, wt. Suitable lead corrosion inhibitors are C, to C 4 alkyl gallates, neopentylglycol disebacate, sebacic acid and quinizarin. Propyl gallate is preferred.

The additive concentrations quoted in this specification are based on the ester basestock. It is to be understood that the composition may contain more than one member of each of the classes of ingredients specified.

THE BASE OIL The base oil is a hindered polyester of the type described above. By polyester is meant an ester having at least two ester linkages per molecule; it therefore includes diesters such as neopentyl glycol dipelargonate and di(2:2:4-trimethylpentyl) sebacate. The term neutral is used to mean a fully esterified product.

It is to be understood that in the esterification reaction described above there may be used more than one of any of the reactants mentioned e.g. a mixture of monocarboxylic acids and, in any case, the neutral ester product of the esterification reaction will sometimes consist of a mixture of different ester molecules, so the expression polyester is to be construed in this light.

Examples of suitable acids and alcohols that may be used in the preparation of the polyester are caprylic acid, capric acid, caproic acid, enanthic acid, pelargonic acid, valeric acid, pivalic acid, propionic acid, butyric acid, 2-ethylhexanoic acid, adipic acid, sebacic acid, azelaic acid, 2;2:4-trimethylpentanol, neopentyl, alcohol, neopentyl glycol, trimethylolethane, trimethylolpropane, trimethylolbutane, pentaerythritol and dipentaerythritol.

The most suitable polyesters are the esters of trimethylolpropane, trimethylolbutane, trimethylolethane,

pentaerythritol and/or di-pentaerythritol with one or more monocarboxylic acids having 3 to 10 carbon atoms, particularly one or more of those mentioned in the previous paragraph, and more complex esters, for example those prepared from trimethylolpropane, sebacic and/or azelaic acid, and one or more monocarboxylic acids having 3 to 10 carbon atoms, particularly one or more of those mentioned in the previous paragraph. Most suitably, the trimethylolpropane and dicarboxylic acid are reacted in the molar ratio of l 0.05 to 0.75, preferably 1 0.075 to 0.4, the amount of monocarboxylic acid being sufficient to provide a carboxyllhydroxyl balance in the reactants.

THE ANTIOXIDANT Suitable alkylated aromatic amine antioxidants are those of the formula R C H NHC l-LR where the groups R are alkyl groups having up to 14 carbon atoms (not necessarily the same in any given molecule), preferably octyl or nonyl groups. p,p'-Dioctyldiphenylamine is particularly effective. Other suitable alkylated aromatic amines include the monoand di- C, to C alkyl phenyl naphthylamines, phenothiazines, iminodibenzyls and diphenyl phenylenediamines, particularly those in which the alkyl groups are octyl or nonyl groups. However, for best results, it is desirable to use a two-component antioxidant consisting of a blend of i. an alkylated phenyl naphthylamine, particularly a monoor di- C to C alkyl phenyl naphthylamine, e.g. monoor dioctyl or a monoor dinonyl phenyl naphthylamine, and

ii. an alkylated diphenylamine, particularly a monoor di- C to C alkyl diphenylamine, e.g., a dioctyl or .dinonyl diphenylamine.

When using this combination, it is preferred to use in the lubricating composition 0.5 to 4.5, especially 0.5 to 3.5 wt of component (i) and 0.5 to 5.0, especially 1.5 to 4.0, wt of component (ii). Most suitably the weight of component (ii) that is used is between 1 and 10, especially between 2 and 4, times the weight of component (i) that is used. The alkylated diphenylamine is used because of its cleanness in use and longlasting quality. p,p-Dioctyldiphenylamine is particularly preferred. The efficiency of the alkylated diphenylamine antioxidants in accelerated oxidation tests is boosted by an alkylated phenyl naphthylamine, preferably a mono-octyl phenyl naphthylamine. The combination has been found to be very satisfactory for the control of viscosity increase during oxidation tests and gives rise to negligible weights of sludge.

THE COPPER PASSIVATOR Copper passivators are a well-known class of materials, the function of which is to reduce the extent to which metals are corroded by corrosive substances. The copper passivator used in the compositions according to the invention must, of course, be soluble in the basestock. The effect of this additive is to reduce the corrosion on engine components containing copper when exposed to the lubricant for long periods of time at high temperatures and in the presence of air. The effectiveness of metal passivators can be measured by the oxidation/corrosion tests described previously. Copper is the most critical metal involved in such tests and it has been found that if this metal can be effectively passivated, then the corrosion of the other metals present is negligibly small, with the exception of lead.

Suitable classes of copper passivator include:

1. Those of the azole type such as imidazole, pyrazole, criazole and their derivatives, e.g. benzotriazole, methylbenzotriazole, ethylbenzotriazole, butylbenzotriazole, dodecylbenzotriazole, methylene bis benzotriazole and naphthotriazole. 2. Salicylaldehyde semicarbazone and its C to C alkyl derivatives, e.g. methyl and isopropyl Salicylaldehyde semicarbazone. 3. Condensation products of Salicylaldehyde and hydrazine derivatives, and fatty acid salts of such condensation products. A particularly suitable hydrazine derivative is aminoguanidine and suitable fatty acids are those having 2 to 24 carbon atoms.

Particularly effective copper passivators are methylene bisbenzotriazole and salts of lsalicylalaminoguanidine and fatty acids having 13 to 18 carbon atoms, e.g., palmitic acid. Where the lubricant is intended for use in engines containing lead alloy components, it is desirable to include a lead corrosion inhibitor in the blend as described previously.

THE LOAD CARRYING ADDlTlVES the main load carrying additive within the previously specified limits and adding a very small amount of the booster (d), above i.e. the amine salt ofa dialkyl hydrogen phosphate. This additive if used in the absence of the neutral phosphate (0) has only a limited effect on the load carrying properties of the lubricant if used at the low concentration specified but at this concentration in combination with the main load-carrying additive (c) it causes an unexpectedly high increase in load carrying properties. In addition, the amine salt appears to suppress the hydrolytic decomposition of the phosphate additive (c) and thereby improve the hydrolytic stability of the blend. The amine salt (d) has the further advantage that, being neutral, it enables a low initial acidity of the blend to be achieved more easily than when using a dialkyl hydrogen phosphate as a load carrying booster as described in co-pending UK Pat. Application No. 32739/66 corresponding to US. Pat. Application Ser. No. 652,727 and its continuation application Ser. No. 139,180, both of said applications now being abandoned.

Tritolyl phosphate is the preferred main load-carrying additive (c) but other effective ones are triphenyl phosphate, phenyl/tolyl phosphates, trixylyl phosphate, tributyl phosphate, tricyclohexyl phosphate and hindered alkyl phosphates, e.g. tri(tertiarybutylphenyl) phosphate and tri(2,2-dimethy1pentyl) phosphate. Suitable amines that may be used for preparing the neutral amine salt of dialkyl hydrogen phosphate are laurylamine, tetraethylene amine, aniline, the naphthylamines, aminoguanidine, diphenylamine, alkylated diphenylamines (e.g. dioctyl diphenylamine) and N- ethylaniline. Laurylamine is preferred.

If desired, a very small proportion (up to 25 parts per million) of an anti-foam agent may be included in the composition, e.g. a silicone.

. EXAMPLES Six examples (A, B, C, D, E and F) of compositions according to the invention were prepared from the ingredients indicated in Table 1 below. The table also gives the composition (X) of a lubricating composition described in said co-pending U.l(. Pat. Application No. 32739/66 which is considered by the applicants to be the best high temperature synthetic lubricant previously known to them. lt will be seen that composition X is similar to composition A but the laurylammonium dibutyl phosphate of A has been replaced by 0.02% wt of dibutyl hydrogen phosphate (C H O) P(O)OH and the dicyclohexyl phosphite has been replaced by 0.05 wt of dibutyl phosphite (C H O) P(O)H.

The base oils used in the compositions were as follows: Base oil P A complex ester made by esterifying caprylic acid, 1 l l-trimethylolpropane and sebacic acid in the molar ratio of 28 l0 1. Base oil Q A complex ester made by esterifying caprylic acid, 1 1 1- trimethylolpropane and sebacic acid in the molar ratio of 10.7 4.23 :1. Base Oil R A blend of 4 parts by weight of a neutral ester of pentaerythritol and a mixture of C to C straight-chain monocarboxylic acids with one part by weight of a neutral ester of dipentaerythritol and the same mixture of acids. Base oil S An ester made by esterifying pentaerythritol, enanthic acid and 2-ethylhexanoic acid in the molar ratio of 1 3 1.

The additives used in the compositions were as follows:

Antioxidants:

-continued MBBTZ Methylene bis benzotriazole 'l'l'P Tritolylphosphate LADBP Lauryl ammonium dibutylphosphate DCHP Dicyclohexyl phosphite Copper passivator:

Load-carrying 8 test. The specification is for a Type 2 aero turbine oil, i.e., an advanced type of aero turbine oil and its oxidation/corrosion requirements (viz. a viscosity increase of not more than 50% and metal weight changes between additives: DBHP Dibutylihydrogen phosphate +0.3 and O.3 mglcm are very severe. It will be seen DBP =Dibuty p osphitc Lead Corrosion inhibitor: PG Propyl ganme that oils A to F compare very favourably with oils J to Dispersant polymer: DlSP Co-polymer of M and are cleaner. Additionally, oils A to F have much N-vmylpylmhdme and a higher load carrying ability than oils J to M and oils A methacrylate (molecular F f d d h h weight 60,000 to 70.000) Sold to are in act inten e to meet or approac t e rec om egc ly lg the name 10 quirements (as at present understood) of the latest cry Hydrolytic stability improver: BMAMP= 2:6ditertiarybutyl-4 Bnllsh Speclficanons f advanced ae ro Olls dimethylaminowhich call for much higher load carrying ability than methylphem' the American specification. The only other oils meet- TABLE 1 Composition A B C D E F X Base oil P 100 100 100 100 Base oil 0 l00 Base oil R 100 Base oil S l00 DODPA 3.0 3.0 3.0 3.0 3.0 3.0 3.0 OPBNA 1.0 1.0 1.0 1.0 1.0 1.0 OPANA 0.5 MBBTZ 0.02 0.02 0.02 0.02 0.02 0.02 0.02 'ITP 2.0 2.0 2.0 2.0 2.0 2.0 2.0 LADBP 0.05 0.05 0.05 0.05 0.05 0.05 DCHP 0.05 0.05 0.05 0.05 0.05 0.05 DBHP 0.02 DBP 0.05 PG 0.1 0.1 0.1 0.1 0.1 0.1 0.1 DISP 0.2 0.2 0.2 0.2 0.2 0.2 BMAMP 0.05

The figures represent parts by weight. The compositions had the physical properties shown in Table 2.

Table 2 A B C D E F X Viscosity at 210F Centistokes 5.41 5.49 5.27 7.36 5.30 5.32 5.49 Viscosity at 100F Centistokes 29.02 29.29 27.85 44.96 29.05 30.93 29.29 Viscosity at 40F Centistokes 9634 8904 l5900 9778 ASTM slope (210 100F) 0.703 0.698 0.704 0.667 0.716 0.730 0.698 Pour Point F 70 70 75 -65 70 70 70 Flash Point (Cleve- "F 505 505 505 505 515 510 land open cup) Acidity mg KOH/g 0.35 0.32 0.35 0.30 0.35 0.35 0.7

T P evaluated Oxldauon ing the load carrying requirements of these British bility. corrosion resistance, load carrying, hydrolyt c specfications known to the applicants are those stability and cleanliness by using tests of the type speci- 45 scribed in co pending UK Pat Application No m governmfmt and engmmanufacturgsi F 32741/66 corresponding to U.S. Pat. Application Ser. cations for lubricants for use in aero turbine engines 652,697 (now abandoned) and its continuation sultable for Jct plication Ser. No. 130,184 new us. Pat. No. Oxidation/Corrosion Test 50 3,790,481. An example of such an oil is composition of Table 3 (equivalent to composition B of said Appli- T test was earned as dsscnbed prevfously cation No. 32741/66). Composition Y meets both the usmg a temperatur'e of 425 F 2 a test Penod of load carrying and oxidation/corrosion requirements of 48 hours and an of 5 [mes/hourthe British specifications but it will be seen that it is T l are table 3 f Shows the outside the oxidation/corrosion limits of the American desirable limits for 0115 of the type in question. Table 3 55 Specification whereas oils A to F are comfortabw also gives results obtained on four commercially availwithin these limits able aero gas turbme L M that have been Oils A to F compare favourably in this test with oil X. approved against an American engine manufacturers specification that contains this oxidation/corrosion Table 3 A B C D E F x .l K L M Y Desirable limits Viscosity increase 41 4| 37 34 40 42 38 47 31.5 24.5 35 54 Not more at 38C than 50 Acidity increase 3.5 2.8 4.7 5.0 1.9 4.8 2.4 2.5 1.5 2.0 2.2 4.5 Not more mg KOH/g than 5 Mg wt change +0.01 0.07 0.01 0.11 0.01 0.22 +0.01 7.1 Nil +0.02 0.02 0.03

mg/cm Al Wt change +0.02 +0.01 0.03 0.02 0.02 0.09 +0.02 0.02 +0.03 0.01 Nil 0.03

Table 3-continued A B C D E F X J K L M Y Desirable limits mg/cm Cu wtchange 41.09 004 -0.02 Nil 41.08 023 003 1.9 003 026 008 064 +0310 mg/cm Ag wtchange -0.03 0.03 +0.03 003 -0.05 -0.03 Nil Nil Nil Ni] 0.01 0.03 0.3

mg/cm Fewt change +002 Nil +0.02 0.0l +0.03 0.02 +0.0l 0.02 +0.02 +0.03 +0.02 +0.04

mg/cm lnsolubles mg Nil Nil Nil Nil Nil Nil Nil 1 5 2.3 Trace Nil Hydrolytic Stability Test Table 6 This test is designed to simulate storage of the oils cmposmn A B C X under the worst possible conditions, i.e. high humidity Weight Loss mg/sq. in. +0.42 0.73 +0.28 1.95

Table 4 Composition A B C X Time to reach acidity of 53 100 53 22 1.5 mg KOH/g hrs.

Panel Coking Test The general cleanliness of the lubricating composition was further assessed by this test in which a sample of the oil is splashed on to a weighed aluminium panel heated to 600F (316C) for 8 hours and the nature and weight of deposit on the panel are noted.

An oil giving a deposit of not more than 10 mg is considered to be an exceptionally good oil of the type in question. Results are given in Table 7 together with the results obtained on commercial oils J, K, L and M and on oils X and Y. It will be seen that the oils according to the invention were much cleaner than the other oils.

Load Carrying Test Table 7 This test employed the well-known IAE Gear Ma- Composition Wt. of deposit chine in which a set of gears is sprayed with the oil being tested at certain elevated temperatures and the A 3 gears are run at 2000 rpm while a load is applied. The B 5 C 7.5 load when scuffing of the gears occurs ls noted. Results D g are given in Table 5. E 2- Table 5 J 79 K 82 Composition A B C D L 74 M 13 Scuffing Load 110C, 2000 rpm. lb. 77 27 80 X 9 Scuffing Load 200C, 2000 rpm. lb. 82 80 85 80 Y 10 Oils A, B, C and D meet or approach the very severe We claim:

load carrying requirements (as at present understood) of the latest British specifications for advanced aero gas turbine lubricants for supersonic transport aircraft. These load carrying requirements are more severe than those in the previously mentioned American specification for a Type 2 oil against which oils J, K, L and M have been approved. No oils have been approved against the British specifications in question at the present time (March 1968).

Lead Corrosion Test This was measured by maintaining a sample of the oil at 375F (190C) for 5 hours with air bubbling through it at a rate of 28 litres per hour and with a copper plate immersed in the oil. A lead plate is rotated in the oil and the weight loss after the -test is measured. A good oil of the type in question is considered to be one which gives a weight loss not exceeding 6.0 mg/sq. in. Results are given in Table 6.

1. A lubricating composition comprising an ester basestock consisting of a liquid neutral polyester that has been prepared by reacting together under esterit'lcation conditions and in at least one stage i. an aliphatic alcohol selected from the group consisting of monohydric alcohols, polyhydric alcohols, and mixtures thereof, said alcohol having 5 to 10 carbon atoms per molecule and having no hydrogen atoms attached to any carbon atom in a 2 position with respect to any OH group and ii. an aliphatic acid selected from the group consisting of monocarboxylic acid, polycarboxylic acid, and mixtures thereof, said acid having 3-12 carbon atoms per molecule,

the basestock having dissolved therein:

a. 1.0 to 8.0% wt of an alkylated aromatic amine antioxidant, said antioxidant selected from the group consisting of mono-C to C alkyl phenyl naphthylamines di-C to C alkyl phenyl naphthylamines,

1 l phenothiazines, iminodibenzyls and diphenyl phenylenediamines, and mixtures of the foregoing,

b. 0.005 to 1.5% wt of a copper passivator, said passivator selected from the group consisting of azole, derivatives thereof, salicylaldehyde semicarbazone, C to C alkyl derivatives thereof, condensation products of salicylaldehyde and hydrazine derivatives, and fatty acid salts of such condensation products,

c. 0.5 to 5.0% wt of a neutral organic phosphate -of the formula (RO) PO where the groups R are tolyl, phenyl or xylyl groups or alkyl groups having up to 10 carbon atoms or cycloalkyl groups having up to 10 carbon atoms, and

d. 0.005 to 0.5% wt of a neutral salt of a dialkyl hydrogen phosphate of the formula (RO) P(O)OH, where R is an alkyl group having up to 10 carbon atoms or a cycloalkyl group having up to 10 carbon atoms, and an amine having not more than 30 carbon atoms.

2. A lubricating composition comprising an ester basestock consisting of a liquid neutral polyester that has been prepared by reacting together under esterification conditions and in at least one stage i. an aliphatic alcohol selected from the group consisting of monohydric alcohols, polyhydric alcohols, and mixtures thereof, said alcohol having 5 to carbon atoms per molecule and having no hydrogen atoms attached to any carbon atom in a 2 position with respect to any OH group and ii. an aliphatic acid selected from the group consisting of monocarboxylic acid, polycarboxylic acid, and mixtures thereof, said acid having 3-12 carbon atoms per molecule,

the basestock having dissolved therein:

a. 1.0 to 8.0% wt of an alkylated aromatic amine antioxidant, said antioxidant selected from the group consisting of mono-C, to C alkyl phenyl naphthylamines, diC to C alkyl phenyl naphthylamines, phenothiazines, iminodibenzyls and diphenyl phenylenediamines, and mixtures of the foregoing,

b. 0.005 to 1.5% wt of a copper passivator, said passivator selected from the group consisting of azole, derivatives thereof, salicylaldehyde semicarbazone, C, to C alkyl derivatives thereof, condensation products of salicylaldehyde and hydrazine derivatives, and fatty acid salts of such condensation products,

c. 0.5 to 5.0% wt of a neutral organic phosphate of the formula (RO PO where the groups R are tolyl, phenyl or xylyl groups or alkyl groups having up to 10 carbon atoms or cycloalkyl groups having up to 10 carbon atoms,

(1. 0.005 to 0.5% wt of a neutral salt of a dialkyl hydrogen phosphate of the formula (RO) P(O)OH, where R is an alkyl group having up to 10 carbon atoms or a cycloalkyl group having up to 10 carbon atoms, and an amine having not more than 30 carbon atoms, and

e. 0.005 to 0.2% wt of a dialkyl phosphite of the formula (R O) P(O)H where R is an alkyl group having up to 10 carbon atoms or a cycloalkyl group having up to 10 carbon atoms.

3. A lubricating composition according to claim 1, in which the polyester is an ester of an alcohol selected from the group consisting of trimethylolpropane, trimethylolethane, trimethylolbutane, pentaerythritol, dipentaerythritol and mixtures thereof with one or more monocarboxlyic acids having 3 to 10 carbon 4. A lubricating composition according to claim 1, in which the polyester is a complex ester prepared from (a) trimethylolpropane, (b) a dibasic acid selected from the group consisting of sebacic acid, azelaic acid, and mixtures of said acids and (c) one or more monocarboxylic acids having 3 to 10 carbon atoms.

5. A lubricating composition according to claim 1 in which the antioxidant is one of the formula R C H Nl-lC l-l R where the groups R are alkyl groups having up to 14 carbon atoms.

6. A lubricating composition according to claim 1, in which the antioxidant is a blend of i. a compound selected from the group consisting of a mono-C to C alkyl phenyl naphthylamine, a di-C to C alkyl phenyl naphthylamine, and

ii. a compound selected from the group consisting of a mono-C to C alkyl diphenylamine and a di-C to C alkyl diphenylamine, the amount of (i) being 0.5 to 4.5% wt and of (ii) being 2.0 to 6.0% wt.

7. A lubricating composition according to claim 6, in which component (i) is selected from the group consisting of mono-octyl phenyl naphthylamine, di-octyl phenyl naphthylamine, mono-nonyl phenyl naphthylamine and di-nonyl phenyl naphthylamine, and component (ii) is selected from the group consisting of dioctyl diphenylamine and dinonyl diphenylamine.

8. A lubricating composition according to claim 1, in which component (b) is selected from the group consisting of methylene benzotriazole, benzotriazole, methyl benzotriazole, ethyl benzotriazole, a salt of lsalicylalaminoguanidine, with at least one fatty acid having 13 to 18 carbon atoms, and mixtures of the foregoing, the weight of (b) being 0.005 to 0.5%.

9. A lubricating composition according to claim 1, in which additive (c) is selected from the group consisting of tritolylphosphate, triphenyl phosphate, a phenyl/tolyl phosphate phosphate mixture, trixylyl phosphate, tributyl phosphate, tricyclohexyl phosphate and a hindered alkyl phosphate, the weight of (0) being 0.5 to 3.5%.

10. A lubricating composition according to claim 1, in which component (d) is a neutral salt of dibutyl or dicyclohexyl hydrogen phosphate and an amine selected from the group consisting of laurylamine, tetraethylene amine, aniline, a naphthylamine, aminoguanidine, diphenylamine, an alkylated diphenylamine and N-ethylaniline, the weight of (d) being 0.01 to 0.1%.

I 1. A lubricating composition according to claim 10, in which the dialkylphosphite is selected from the group consisting of dibutyl phosphite and dicyclohexyl phosphite, the amount being 0.01 to 0.1% wt.

12. A lubricating composition according to claim 1, which also contains 0.01 to 5.0% wt of a dispersant polymer selected from the group consisting of acrylate polymers, methacrylate polymers, co-polymers of N- vinyl pyrrolidone with acrylates and methacrylates, and co-polymers of N-vinyl pyrrolidone with an olefin.

13. A lubricating composition according to claim 12, in which the dispersant polymer is a polymer or copolymer having a molecular weight of 1000 to 1,000,000 and being present in an amount of 0.01 to 1.0% wt.

14. A lubricating composition according to claim 1, which also contains 0.01 to 1.0% wt of a lead corrosion inhibitor selected from the group consisting of C to C alkyl gallates, neopentylglycol disebacate, sebacic acid 13 and quinizarin.

15. A lubricating composition according to claim 14, in which the lead corrosion inhibitor is present in an amount of 0.05 to 0.25% wt.

16. A lubricating composition according to claim 1, which also contains 0.005 to 0.5% wt of a hydrolytic stability improver, said improver being an amine having the general formula R (R )NR where R and R are alkyl groups having 1 to 4 carbon atoms and R is an alkaryl, or hydroxy-substituted alkaryl, group having up to 20 carbon atoms.

17. A lubricating composition according to claim 16, in which the hydrolytic stability improver is present in the amount of 0.02 to 0.1% wt.

18. A lubricating composition comprising an ester basestock consisting of a liquid neutral polyester prepared by reacting (a) one molar proportion of trimethylolpropane, (b) 0.075 to 0.4 molar proportions of a dibasic acid selected from the group consisting of sebacic acid and azelaic acid, and (c) sufficient of one or more monocarboxylic acids having 3 to 10 carbon atoms to provide a hydroxyl/carboxyl balance in reactants, the said polyester having dissolved therein:

a. 0.5 to 3.5% wt of a naphthylamine selected from the group consisting of mono-octyl phenyl naphthylamine, di-octyl phenyl naphthylamine, monononyl phenyl naphthylamine, di-nonyl phenyl naphthylamine, and mixtures of the foregoing,

b. 1.5 to 4.0% wt of dioctyl or dinonyl diphenylamine, the total weight of (a) and (b) being between 3.0 and 5.0%,

c. 0.005 to 0.5% wt of methylene bis benzotriazole,

d. 1.0 to 3.0% wt of tritolyl phosphate,

0.01 to 0.1% wt of a neutral salt of dibutyl hydrogen phosphate and laurylamine,

f. 0.01 to 0.1% wt of dicyclohexyl phosphite and g. 0.05 to 0.25% wt of propyl gallate.

19. A lubricating composition comprising an ester basestock consisting of a liquid neutral polyester prepared by reacting pentaerythritol, either alone or in admixture with up to 50% by weight of di-pentaerythritol, with the stoichiometric amount of one or more monocarboxylic acids having 3 to 10 carbon atoms, the said polyester having dissolved therein:

a. 0.5 to 3.5% wt of a mono-octyl phenyl naphthylamine, di-octyl phenyl naphthylamine, or a monononyl phenyl naphthylamine, di-nonyl phenyl naphthylamine, or mixtures of the foregoing,

b. 1.5 to 4.0% wt of a dioctyl or a dinonyl diphenylamine, the total weight of (a) and (b) being 3.0 and 5.0%,

c. 0.005 to 0.5% wt of methylene bis benzotriazole,

d. 1.0 to 3.0% wt of tritolyl phosphate,

e. 0.01 to 0.1% wt of a neutral salt of dibutyl hydrogen phosphate and laurylamine,

f. 0.01 to 0.1% wt of dicyclohexyl phosphite and g. 0.05 to 0.25% wt of propyl gallate.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION PATENT NO. 1 3 914, 179 D T I October 21, 1975 INVENTOR(S) Derek Clark Byford and Anthony Arnold John Mundye It is certified that error appears in the ab0ve-identified patent and that said Letters Patent are hereby corrected as shown below:

Page 1, line 12 (to the right of code [63]) change "continuation-in-part" to continuation Signed and Scaled this tenth D3) 0f February 1976 sen A ttes t:

RUTH C. MAnsoN C. MARSHALL DANN Atrestrng Ofjrcer Commissioner uj'latenls and Trademarks 

1. A LUBRICATING COMPOSITION COMPRISING AN ESTER BASESTOCK CONSISTING OF A LIQUID NEUTRAL POLYESTER THAT HAS BEEN PREPARED BY REACTING TOGETHER UNDER ESTERIFICATION CONDITIONS AND IN AT LEAST ONE STAGE I. AN ALIPHATIC ALCOHOL SELECTED FROM THE GROUP CONSISTING OF MONOHYDRIC ALCOHOLS, POLYHYDRIC ALCOHOLS, AND MIXTURES THEREOF, SAID ALCOHOL HAVING 5 TO 10 CARBON ATOMS PER MOLECULE AND HAVING NO HYDROGEN ATOMS ATTACHED TO ANY CARBON ATOM IN A 2 POSITION WITH RESPECT TO ANY -OH GROUP AND II. AN ALIPHATIC ACID SELECTED FROM THE GROUP CONSISTING OF MONOCARBOXYLIC ACID, POLYCARBOXYLIC ACID, AND MIXTURES THEREOF, SAID ACID HAVING 3-12 CARBON ATOMS PER MOLECULE, THE BASESTOCK HAVING DISSOLVED THEREIN:, A. 1.0 TO 8.0% WT OF AN ALKYLATED AROMATIC AMINE ANTIOXIDANT, SAID ANTIOXIDANT SELECTED FROM THE GROUP CONSISTING OF MONO-C1 TO C14 ALKYL PHENYL NAPHTHYLAMINES DI-C1 TO C14 ALKYL PHENYL NAPHTHYLAMINES, PHENOTHIAZINES, IMINODIBENZYLS AND DIPHENYL PHENYLENEDIAMINES, AND MIXTURES OF THE FOREGOING, B. 0.005 TO 1.5% WT OF A COPPER PASSIVATOR, SAID PASSIVATOR SELECTED FROM THE GROUP CONSISTING OF AZOLE, DERIVATIVES THEREOF, SALICYLALDEHYDE SEMICARBAZONE, C1 TO C20 ALKYL DERIVATIVES THEREOF, CONDENSATION PRODUCTS OF SALICYLALDEHYDE AND HYDRAZINE DERIVATIVES, AND FATTY ACID SALTS OF SUCH CONDENSATION PRODUCTS, C. 0.5 TO 5.0% WT OF A NEUTRAL ORGANIC PHOSPHATE OF THE FORMULA (RO)3PO WHERE THE GROUPS R ARE TOLYL, PHENYL OR XYLYL GROUPS OR ALKYL GROUPS HAVING UP TO 10 CARBON ATOMS OR CYCLOALKYL GROUPS HAVING UP TO 10 CARBON ATOMS, AND D. 0.005 TO 0.5% WT OF A NEUTRAL SALT OF A DIALKYL HYDROGEN PHOSPHATE OF THE FORMULA (R1O)2P(O)OH, WHERE R IS AN ALKYL GROUPS HAVING UP TO 10 CARBON ATOMS OR A CYCLOALKYL GROUP HAVING UP TO 10 CARBON ATOMS, AND AN AMINE HAVING NOT MORE THAN 30 CARBON ATOMS.
 2. A lubricating composition comprising an ester basestock consisting of a liquid neutral polyester that has been prepared by reacting together under esterification conditions and in at least one stage i. an aliphatic alcohol selected from the group consisting of monohydric alcohols, polyhydric alcohols, and mixtures thereof, said alcohol having 5 to 10 carbon atoms per molecule and having no hydrogen atoms attached to any carbon atom in a 2 position with respect to any -OH group and ii. an aliphatic acid selected from the group consisting of monocarboxylic acid, polycarboxylic acid, and mixtures thereof, said acid having 3-12 carbon atoMs per molecule, the basestock having dissolved therein: a. 1.0 to 8.0% wt of an alkylated aromatic amine antioxidant, said antioxidant selected from the group consisting of mono-C1 to C14 alkyl phenyl naphthylamines, di-C1 to C14 alkyl phenyl naphthylamines, phenothiazines, iminodibenzyls and diphenyl phenylenediamines, and mixtures of the foregoing, b. 0.005 to 1.5% wt of a copper passivator, said passivator selected from the group consisting of azole, derivatives thereof, salicylaldehyde semicarbazone, C1 to C20 alkyl derivatives thereof, condensation products of salicylaldehyde and hydrazine derivatives, and fatty acid salts of such condensation products, c. 0.5 to 5.0% wt of a neutral organic phosphate of the formula (RO)3PO where the groups R are tolyl, phenyl or xylyl groups or alkyl groups having up to 10 carbon atoms or cycloalkyl groups having up to 10 carbon atoms, d. 0.005 to 0.5% wt of a neutral salt of a dialkyl hydrogen phosphate of the formula (R1O)2P(O)OH, where R1 is an alkyl group having up to 10 carbon atoms or a cycloalkyl group having up to 10 carbon atoms, and an amine having not more than 30 carbon atoms, and e. 0.005 to 0.2% wt of a dialkyl phosphite of the formula (R2O)2P(O)H where R2 is an alkyl group having up to 10 carbon atoms or a cycloalkyl group having up to 10 carbon atoms.
 3. A lubricating composition according to claim 1, in which the polyester is an ester of an alcohol selected from the group consisting of trimethylolpropane, trimethylolethane, trimethylolbutane, pentaerythritol, dipentaerythritol and mixtures thereof with one or more monocarboxlyic acids having 3 to 10 carbon atoms.
 4. A lubricating composition according to claim 1, in which the polyester is a complex ester prepared from (a) trimethylolpropane, (b) a dibasic acid selected from the group consisting of sebacic acid, azelaic acid, and mixtures of said acids and (c) one or more monocarboxylic acids having 3 to 10 carbon atoms.
 5. A lubricating composition according to claim 1 in which the antioxidant is one of the formula R3C6H4NHC6H4 R3 where the groups R3 are alkyl groups having up to 14 carbon atoms.
 6. A lubricating composition according to claim 1, in which the antioxidant is a blend of i. a compound selected from the group consisting of a mono-C1 to C14 alkyl phenyl naphthylamine, a di-C1 to C14 alkyl phenyl naphthylamine, and ii. a compound selected from the group consisting of a mono-C1 to C14 alkyl diphenylamine and a di-C1 to C14 alkyl diphenylamine, the amount of (i) being 0.5 to 4.5% wt and of (ii) being 2.0 to 6.0% wt.
 7. A lubricating composition according to claim 6, in which component (i) is selected from the group consisting of mono-octyl phenyl naphthylamine, di-octyl phenyl naphthylamine, mono-nonyl phenyl naphthylamine and di-nonyl phenyl naphthylamine, and component (ii) is selected from the group consisting of dioctyl diphenylamine and dinonyl diphenylamine.
 8. A lubricating composition according to claim 1, in which component (b) is selected from the group consisting of methylene benzotriazole, benzotriazole, methyl benzotriazole, ethyl benzotriazole, a salt of 1-salicylalaminoguanidine, with at least one fatty acid having 13 to 18 carbon atoms, and mixtures of the foregoing, the weight of (b) being 0.005 to 0.5%.
 9. A lubricating composition according to claim 1, in which additive (c) is selected from the group consisting of tritolylphosphate, triphenyl phosphate, a phenyl/tolyl phosphate phosphate mixture, trixylyl phosphate, tributyl phosphate, tricyclohexyl phosphate and a hindered alkyl phosphate, the weight of (c) being 0.5 to 3.5%.
 10. A lubricating composition according to claim 1, in which component (d) is a neutral salt of dibutyl or dicyclohexyl hydrogen phosphate and an amine selected from the group consisting of laurylamine, tetraethylene amine, aniline, a naphthylamine, aminoguanidine, diphenylamine, an alkylated diphenylamine and N-ethylaniline, the weight of (d) being 0.01 to 0.1%.
 11. A lubricating composition according to claim 10, in which the dialkylphosphite is selected from the group consisting of dibutyl phosphite and dicyclohexyl phosphite, the amount being 0.01 to 0.1% wt.
 12. A lubricating composition according to claim 1, which also contains 0.01 to 5.0% wt of a dispersant polymer selected from the group consisting of acrylate polymers, methacrylate polymers, co-polymers of N-vinyl pyrrolidone with acrylates and methacrylates, and co-polymers of N-vinyl pyrrolidone with an olefin.
 13. A lubricating composition according to claim 12, in which the dispersant polymer is a polymer or co-polymer having a molecular weight of 1000 to 1,000,000 and being present in an amount of 0.01 to 1.0% wt.
 14. A lubricating composition according to claim 1, which also contains 0.01 to 1.0% wt of a lead corrosion inhibitor selected from the group consisting of C1to C20 alkyl gallates, neopentylglycol disebacate, sebacic acid and quinizarin.
 15. A lubricating composition according to claim 14, in which the lead corrosion inhibitor is present in an amount of 0.05 to 0.25% wt.
 16. A lubricating composition according to claim 1, which also contains 0.005 to 0.5% wt of a hydrolytic stability improver, said improver being an amine having the general formula R4(R5)NR6, where R4 and R5 are alkyl groups having 1 to 4 carbon atoms and R6 is an alkaryl, or hydroxy-substituted alkaryl, group having up to 20 carbon atoms.
 17. A lubricating composition according to claim 16, in which the hydrolytic stability improver is present in the amount of 0.02 to 0.1% wt.
 18. A lubricating composition comprising an ester basestock consisting of a liquid neutral polyester prepared by reacting (a) one molar proportion of trimethylolpropane, (b) 0.075 to 0.4 molar proportions of a dibasic acid selected from the group consisting of sebacic acid and azelaic acid, and (c) sufficient of one or more monocarboxylic acids having 3 to 10 carbon atoms to provide a hydroxyl/carboxyl balance in reactants, the said polyester having dissolved therein: a. 0.5 to 3.5% wt of a naphthylamine selected from the group consisting of mono-octyl phenyl naphthylamine, di-octyl phenyl naphthylamine, mono-nonyl phenyl naphthylamine, di-nonyl phenyl naphthylamine, and mixtures of the foregoing, b. 1.5 to 4.0% wt of dioctyl or dinonyl diphenylamine, the total weight of (a) and (b) being between 3.0 and 5.0%, c. 0.005 to 0.5% wt of methylene bis benzotriazole, d. 1.0 to 3.0% wt of tritolyl phosphate, 0.01 to 0.1% wt of a neutral salt of dibutyl hydrogen phosphate and laurylamine, f. 0.01 to 0.1% wt of dicyclohexyl phosphite and g. 0.05 to 0.25% wt of propyl gallate.
 19. A lubricating composition comprising an ester basestock consisting of a liquid neutral polyester prepared by reacting pentaerythritol, either alone or in admixture with up to 50% by weight of di-pentaerythritol, with the stoichiometric amount of one or more mono-carboxylic acids having 3 to 10 carbon atoms, the said polyester having dissolved therein: a. 0.5 to 3.5% wt of a mono-octyl phenyl naphthylamine, di-octyl phenyl naphthylamine, or a mono-nonyl phenyl naphthylamine, di-nonyl phenyl naphthylamine, or mixtures of the foregoing, b. 1.5 to 4.0% wt of a dioctyl or a dinonyl diphenylamine, the total weight of (a) and (b) being 3.0 and 5.0%, c. 0.005 to 0.5% wt of methylene bis benzotriazole, d. 1.0 to 3.0% wt of tritolyl phosphate, e. 0.01 to 0.1% wt of a neutral salt of dibutyl hydrogen phosphate and laurylamine, f. 0.01 to 0.1% wt of dicyclohexyl phosphite and g. 0.05 to 0.25% wt of propyl gallate. 